1. Field of the Invention:
The present invention relates in general to instrumentation for and methods of implanting a spherical prosthesis in a joint between a first bone and a second bone, and more specifically to instrumentation for and a method of implanting a spherical prosthesis in the carpometacarpal joint of a patient's thumb.
2. Information Disclosure Statement:
Various prostheses and methods have heretofore been developed for the replacement of damaged bones, skeletal articular surfaces and joints, including the bones of the human wrist and hand. For example, Metcalfe, J. W.: "Vitallium Sphere Prosthesis for Nonunion of the Navicular Bone"; Journal of the International College of Surgeons, 22: 459-462, 1954, and Legge, R. F.: "Vitallium Prosthesis in the Treatment of Fracture of the Carpal Navicular"; The Western Journal of Surgery, Obstetrics & Gynecology, 59: 468-471, September, 1951, disclose vitallium sphere prostheses for the complete replacement of a fractured scaphoid (navicular) bone.
The articular surfaces between the trapezium and the first, or thumb, metacarpal in a person's hand will sometimes degenerate due to conditions such as osteoarthritis or trauma, resulting in severe pain during thumb circumduction, etc. Clift et al., U.S. Pat. No. 5,326,364, issued Jul. 5, 1994, discloses a trapezial implant for replacing the distal surface of a trapezium. The method disclosed by Clift et al. includes exposing the carpometacarpal joint of the patient's thumb through a transverse or curved longitudinal incision; then resecting the distal end or saddle of the trapezium with an osteotome or power sagittal saw to create a flat distal surface; and then attaching a trapezial implant to the flat distal surface of the prepared trapezium by forcing a pair of pointed posts extending from the back side of the trapezial implant into the flat distal surface of the prepared trapezium.
Nothing in the known prior art discloses or suggests the present invention. More specifically, nothing in the known prior art discloses or suggests a method including the steps of exposing a joint between a first bone and a second bone; forming a semispherical cavity (e.g., a cavity substantially equal to an outer 1/3 of a sphere) in the proximal surface of the first bone; forming a semispherical cavity (e.g., a cavity substantially equal to an outer 1/3 of a sphere) in the distal surface of the second bone; and inserting a spherical prosthesis into the semispherical cavities in the proximal surface of the first bone and in the distal surface of the second bone. Likewise, nothing in the known prior art discloses or suggests a cutting instrument including a cutting instrument head having the shape of a segment of a sphere with at least one truncated end or side, and a shaft attached to the cutting instrument head for allowing the cutting instrument head to be inserted between the proximal end of a first bone and the distal end of a second bone, and to be then at least partially rotated about a rotational axis generally transverse to an axis or plane extending through the center of the segment of a sphere substantially perpendicular to the plane of the surface of the truncated end or side thereof; or a trial instrument including a trial instrument head having the shape of a segment of a sphere with a truncated end, and a shaft attached to the trial instrument head for allowing the trial instrument head to be inserted into semispherical cavities in the proximal end of a first bone and the distal end of a second bone, and to be then rotated about a rotational axis generally transverse to an axis extending through the center of the segment of a sphere substantially perpendicular to the plane of the surface of the truncated end or side thereof.